Hello,

Yes, you can appear for NDA entrance exam when you are appearing in the qualifying exam that is class 12th but you must obtain your result and pass in all subjects at the time of SSB Interview. If you qualify in the NDA entrance exam you will have to attend for SSB interview and on the first day of the SSB interview the original documents will be verified and you must provide the qualifying exam certificate on that day only then you will be considered for next stage of the interview if not you cannot attend for next stage of the interview.